Effects of Soil Moisture Variability on Morphological and Anatomical Attributes of Roots and Buds of Selected Rangeland Grasses of Southern Rangelands of Kenya

Abstract

This study evaluated the morphological and anatomical responses of below-ground parts of Pennisetum mezianum, Digitaria macroblephara,and Themeda triandra to moisture variation in the semi-arid rangelands of South Eastern Kenya. Bud and root functional traits, including average root diameter (RD), root tissue density (RTD), specific root length (SRL), percent root dry matter content (PRDM), and non-structural carbohydrates (NSC) were determined.Soil moisture content below the ground surface was monitored to determine its relationship with the aforementioned parameters. Decline in soil moisture caused significant (p<0.05) decrease in bud size, PRDM, and increase in NSC for all three grass species. Generally, RTD increased with increase in soil moisture deficit in all three grass species. For SRL, it significantly increased with a decrease in soil moisture content in D. macroblephara. There was no significant variation in the average number of buds and RD, with corresponding variation in soil moisture content. Pennisetum mezianum had significantly (p<0.05) higher number of buds, largest bud sizes, largest RD, lowest SRL, lowest RTD, and least amount of NSC content. Themeda triandra and D. macroblephara had a narrow root diameter, high SRL, high RTD, and a high NSC content. These patterns indicate that the three grass species had developed diverse strategies to withstand water deficit conditions, with P. mezianum employing a conservative strategy, while T. triandra and D. macroblephara employ a timely utilization strategy. Further research should be conducted on more range grass species over multiple seasons to better understand adaptive mechanisms of range grass species to enable us to predict plant community change because of climate change.